The use of optical and/or optoelectronic devices is increasing in communications applications. These device often include light sensors that receive light signals from a waveguide. These light sensors often employ a light absorbing material that absorbs light signals. During operation of the light sensor, an electrical field is present across the light absorbing material. When the light absorbing material absorbs a light signal, an electrical current flows through the light absorbing material. As a result, the level of electrical current through the light absorbing material indicates the intensity of light signals being received by the light absorbing material.
These waveguides that are present on optical and/or optoelectronic devices are often made of silicon. Because silicon does not absorb the light signals having the wavelengths that are used in communications applications, silicon is often not effective for use as the light absorbing medium in the light sensors for communications application. In contrast, germanium is a material that can absorb these light signals and is accordingly often used as the light absorbing medium in the light sensors for communications application. However, the use of germanium in combination with silicon waveguides can be associated with undesirably high levels of dark current. Dark current is the flow of electrical current through the light sensor when the light sensor is not receiving light signals. As a result, dark current is a source of noise for these light sensors.
For the above reasons, there is a need for an improved interface between waveguides and light sensors.